Messages in this thread | | | Date | Wed, 23 Feb 2011 10:37:26 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH] debug rcu head support !PREEMPT config |
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* Steven Rostedt (rostedt@goodmis.org) wrote: > On Wed, 2011-02-23 at 10:13 -0500, Mathieu Desnoyers wrote: > > Remove DEBUG_RCU_HEAD dependency on PREEMPT config. Handle the unability to > > detect if within a RCU read-side critical section by never performing any > > attempt to recover from a failure situation in the fixup handlers. Just print > > the warnings. > > > > This patch is only compile-tested. > > > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > > --- > > kernel/rcupdate.c | 17 +++++++++++++++++ > > lib/Kconfig.debug | 2 +- > > 2 files changed, 18 insertions(+), 1 deletion(-) > > > > Index: linux-2.6-lttng/lib/Kconfig.debug > > =================================================================== > > --- linux-2.6-lttng.orig/lib/Kconfig.debug > > +++ linux-2.6-lttng/lib/Kconfig.debug > > @@ -313,7 +313,7 @@ config DEBUG_OBJECTS_WORK > > > > config DEBUG_OBJECTS_RCU_HEAD > > bool "Debug RCU callbacks objects" > > - depends on DEBUG_OBJECTS && PREEMPT > > + depends on DEBUG_OBJECTS > > help > > Enable this to turn on debugging of RCU list heads (call_rcu() usage). > > > > Index: linux-2.6-lttng/kernel/rcupdate.c > > =================================================================== > > --- linux-2.6-lttng.orig/kernel/rcupdate.c > > +++ linux-2.6-lttng/kernel/rcupdate.c > > @@ -142,7 +142,14 @@ static int rcuhead_fixup_init(void *addr > > * Ensure that queued callbacks are all executed. > > * If we detect that we are nested in a RCU read-side critical > > * section, we should simply fail, otherwise we would deadlock. > > + * In !PREEMPT configurations, there is no way to tell if we are > > + * in a RCU read-side critical section or not, so we never > > + * attempt any fixup and just print a warning. > > */ > > +#ifndef CONFIG_PREEMPT > > + WARN_ON(1); > > + return 0; > > +#endif > > if (rcu_preempt_depth() != 0 || preempt_count() != 0 || > > irqs_disabled()) { > > WARN_ON(1); > > @@ -184,7 +191,14 @@ static int rcuhead_fixup_activate(void * > > * Ensure that queued callbacks are all executed. > > * If we detect that we are nested in a RCU read-side critical > > * section, we should simply fail, otherwise we would deadlock. > > + * In !PREEMPT configurations, there is no way to tell if we are > > + * in a RCU read-side critical section or not, so we never > > + * attempt any fixup and just print a warning. > > */ > > +#ifndef CONFIG_PREEMPT > > + WARN_ON(1); > > + return 0; > > +#endif > > if (rcu_preempt_depth() != 0 || preempt_count() != 0 || > > irqs_disabled()) { > > WARN_ON(1); > > @@ -214,6 +228,9 @@ static int rcuhead_fixup_free(void *addr > > * Ensure that queued callbacks are all executed. > > * If we detect that we are nested in a RCU read-side critical > > * section, we should simply fail, otherwise we would deadlock. > > + * In !PREEMPT configurations, there is no way to tell if we are > > + * in a RCU read-side critical section or not, so we never > > + * attempt any fixup and just print a warning. > > */ > > #ifndef CONFIG_PREEMPT > > WARN_ON(1); > > Hmm, I wonder if s/WARN_ON/WARN_ON_ONCE/g is in order. Why spam the > console if it happens to trigger all the time?
The system should die pretty soon anyway due to list corruption, so I don't think it's a problem in practice.
Thanks,
Mathieu
> > -- Steve > >
-- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com
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